The immune reaction is known to be involved in the development of many diseases such as inflammation, tumor, allergy, autoimmune disorders, implantation rejection reaction (graff versus host disease) and the like. However, reduced immune reaction may cause higher susceptibility to infections with various viruses, bacteria and fungus, and can also cause increased incidence of a tumor.
The term "immune-activating agent" was used originally to mean the agents that enhance anti-tumor immunity. Then, the term came to be used to mean the agents that provide recovery from reduced or deteriorated immune system functions caused by foreign factors such as drugs or irradiation, as well as other factors such as acquired immunodeficiency syndrome and malignant tumors. Currently, immune-activating agents are not only used for immuno-therapy of a tumor, but are also used independently or in combination with a recombinant vaccine for the purpose of enhancing non-specific resistance in a host against various infections.
Some immune-activating agents are made from materials that have traditionally been used as folk remedies for the purpose of enhancing non-specific resistance, such as Basidiomycota including Kofukisaruno koshikake fungus (Elfvingia applanata), Meshimakobu-fungus and Shiitake fungus (Lentlinus edodes) as well as Otane ninjin fungus and Eleutherococ. Such fungi are taken orally and are referred to as Japanese and Chinese folk medicines. However, these folk medicines should, instead, be called "immune-enhancing foods" when their effects are viewed immunologically. An immunological study in experimental animals revealed that Basidiomycota organisms exhibited an immunological function-activating effect .sup.1)2) only when administered intraperitoneally or intravenously as extracts or independent ingredients, and that Otaneninjin did not provide such effects..sup.3) Oral administration of these materials provided no immunological function-activating effect. FNT .sup.1) Chihara, Pharmacia Review 6:119 (1981) and references FNT .sup.2) Akiyama and Hamuro, Proteins, Nucleic Acids and Enzymes 26:208 (1981) and references cited therein FNT .sup.3) Hayashi et al., Journal of Kanazawa Medical University, 3:171(1978)
Japanese TOKKYO KOKAI No. 54-80486 discloses a method of artificial incubation of a nonsexual fungus of the family Cordyceps Japonensis and a method of preparing an extract or a powder of an active ingredient from the incubated mycelium. Japanese TOKKYO KOKOKU No. 61-53033, invented by one of the inventors and applicants of the present invention, N. Yahagi, discloses a method of artificial incubation of Cordyceps Japonensis, and describes some nourishing and vitalizing effects, and some anti-cancer effects, of Cordyceps Japonensis.
However, the immune-enhancing foods discussed above, derived from traditional, naturally occurring drugs, have not objectively shown effects in any immunological study in animal experiments. For the purpose of using an immune-enhancing food in a self-controlled therapy in these days, an immune-enhancing food having objectively proven activity is desired.